The photosynthetic culture of microalgae is becoming increasingly popular. This enthusiasm is due to the fact that the microalgae have an exceptional potential for the sequestration of CO2, for the cleanup of wastes, the production of biofuels, and for the production of biosourced products such as pharmaceuticals and foodstuffs.
The approach most often used in the growing of microalgae consists in a monoculture, or the growing of a single species of algae. The monoculture systems generally operate under closed and sterile conditions and are complex, given that they require a close managing of several factors in order to prevent contamination by bacteria and pathogens, and also to ensure an adequate growth of the particular species of algae being grown. The selection of the appropriate type of algae placed in culture is generally critical, in order to maximize the yields associated with the specific use in mind (e.g., either the sequestration of CO2, or the cleanup of wastes, or the production of biofuels, etc.). These culture systems may be also disadvantageous because they require the use of antibiotics or biocides to maintain the characteristics and the performance of the culture.
Some have suggested the possibility of growing indigenous algae for the purpose of boosting the production of biogas. Others have proposed the possibility of cultivating indigenous algae for the local production of biosourced products.
It has also been suggested to grow a consortium of different species of microalgae. For example, some have suggested the screening of individual algae for use in a polyculture system. Others have described the growing of a consortium of microalgae for biomass production and for production of bioenergy. Other references teach using a consortium of two or more species of algae for the production of biomass and/or for production of particular algal lipid, proteins, carbohydrates constituents. However, no one discloses controlling the culture conditions for affecting either flocculation and/or settling of the consortium of microalgae or either for affecting adhesion of the microalgae to surfaces of the bioreactor.
Cultivation of algae under conditions in which the cells become deficient in nitrogen, thereby causing the cells to produce long chain polymers having flocculating properties is known in the art. However, the culture of a consortium of multiples algal species, while controlling the properties of the algal cells to affect their flocculation and/or settling or to affect adhesion of the algal cells to surfaces of the reactor is not known in the art.
Thus, there exists a need for more robust, more easily parametrable, and controllable methods and systems for the culture of microalgae. In particular, there is a need for methods and systems for culturing and growing a consortium of microalgae in non-sterile cultures conditions, especially for the production of microalgae having properties and characteristics that can be adjusted and adapted as a function of proposed applications and desired results. More particular examples of desired controllable properties includes promoting flocculation and/or settling of the consortium of microalgae and/or minimizing adhesion of the microalgae to surfaces of the bioreactor or its components (e.g. optical elements). Controlling these properties may facilitate and/or promote harvesting of microalga and/or optimize productivity of the culture system. Methods and systems comprising controlling culture conditions for affecting proteins, carbohydrates and/or lipids content of the consortium of microalgae are also desirable.